In order to provide an accurate and sensitive analytical scale, the advancement of the balance weight along the balance beam must be accomplished with a minimum of frictional force. Since frictional force is dependent upon the normal force exerted by the balance weight upon the beam, it was conceived to support the balance weight in rolling movement upon the beam.
This scheme was sufficient to eliminate friction effects, but introduced the problem of backlash in the lead screw connection. In other words, some force in the lead screw connection was still necessary to provide accurate coupling between the balance weight and the lead screw drive. The invention was conceived as an adjustable coupling device for the aforementioned connection, which would provide a predetermined force or pressure.